This invention relates to certain organometallic compounds and the preparation thereof and, more specifically, is directed to certain novel organobarium, organocalcium and organostrontium compounds and processes for making such compounds.
It has heretofore been known that certain barium alkoxides in conjunction with alkyllithium or dialkylmagnesium compounds promote the polymerization and copolymerization of, for example, 1,3-butadiene to a polymer having a high trans-1,4 microstructure and possessing unique beneficial properties in its use as a tire rubber.
It has also heretofore been known that the barium or calcium compounds, particularly for the foregoing purposes, must be present as an alkoxide and that, generally, the barium or calcium alkoxide interacts strongly with the alkyllithium or dialkylmagnesium compounds to form complexes of, presumably, alkylbarium or alkylcalcium alkoxides with the alkyllithium or dialkylmagnesium compounds.
For maximum efficiency in this interchange reaction and for use as a polymerization initiator, it is particularly advantageous to employ barium alkoxides which possess a high solubility in liquid hydrocarbon media. Initial experimental work was done utilizing barium tert-butoxide (A. Onishi et al, U.S. Pat. No. 3,629,213, Dec. 21, 1971). However, barium tert-butoxide, by itself, was found to possess a low order of solubility in liquid aliphatic hydrocarbon solvents (U.S. Pat. No. 4,044,900, July 5, 1977); while barium ethoxide is even less soluble (Z. M. Baydakova, et al (a) High Molecular Wt. Compounds 1976 Vol. (A) XVIII, No. 9 (Russian) (b) Vysokomol.Soedin. Series B 1977, 19 (10) 767-70 (Russian). Later, others (U.S. Pat. No. 4,355,156) have shown that barium tert-butoxide, in conjunction with barium tert-decanolate and barium hydroxide, has a superior solubility in toluene over barium tert-butoxide-barium hydroxide alone (I. G. Hargis, R. A. Livigni and S. L. Aggarwal, ACS Symposium Series, 1982, No. 193 (Elastomers Rubber Elasticity).
Barium or calcium alkoxides are generally prepared by reacting a solution of barium or calcium metal in liquid ammonia or methylamine, with the desired alcohol, followed by evaporation of the solvent and subsequent drying in vacuo. Solutions of the barium or calcium alkoxides are then made up in the desired hydrocarbon solvent.
It is one of the objects of my invention to make available barium, calcium and strontium alkoxides possessing a particularly high solubility in liquid hydrocarbon solvents, and in the hydrocarbon solutions thereof.
It is another object of my invention to provide a simplified process for the preparation of such barium calcium and strontium alkoxides directly in the hydrocarbon solvents.
Another object of my invention is to provide a novel method of preparing barium, calcium and strontium amides.
A still further object of my invention is to provide a process for the preparation of liquid hydrocarbon-soluble stable complexes of alkylbarium, alkylcalcium and alkylstrontium alkoxides with alkyllithium, dialkylmagnesium with or without trialkylaluminum compounds using, advantageously, barium, calcium or strontium alkoxide solutions.